Efficiency comparison of common geostatistices methods with of fuzzy kriging method in preparing rainfall isoerodent map in namak lake watershed

Environmental data and information could be defined in the formed of fuzzy sets with no defined accurate boundaries. There do not exist any sharply defined boundaries between informational media، and this very specialty better reflects the continuality of natural phenomena. In this research، in the course of preparation of a map of rainfall erosivity in the Namak Lake basin، the accuracies of the several common methods of interpolation Viz: common Kriging، Co-Kriging، Spline، Inverse Distance Weighted، and Fuzzy Kriging have been appraised. The values of EI30 index evaluated through an empirical relationship have been employed as fuzzy numbers. Results reveal “Fuzzy Kriging” (with a mean absolute error of 10. 49) as the most accurate one among all methods. Thin Plate Spline، is on the other hand of the highest mean absolute error. Based upon the map، prepared on the basis of Fuzzy Kriging method minimum and maximum values of EI30 index are recorded as 10. 99 and 233. 73 mega joule mm per ha per hr per year. Rainfall erosivity index values increase towards north of Namak lake basin. The vastest EI30 index area in Namak Lake basin belongs to the values between 80-93 mega joule mm per ha per hr per year with a covering area of 20 percent. Keywords: Geostatistics، Inverse Distance Weighted، Rainfall erosivity index، Co-Kriging،